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    <title>Document</title>
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<script>
    // function  add(num1,num2){
    //     return  num1 +num2;
    // }
    // let result  = add(1,2);
    //console.log(result);
 

    function add(num1,num2,cb){ //cb
        cb(num1+num2);
    }
    add(1,9,(result)=>{
        alert(result);
    });



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